This invention relates to a process for the manufacture of optical glass fiber, and more specifically relates to a novel process in which glass precursor coatings are formed on a continuously moving filamentary core of material which is removed from or becomes an integral part of the ultimately formed optical fiber.
Optical glass fiber is commonly used as the radiation conductor of optical communication or signal-processing systems. Known processes for manufacture of optical fibers employ a thick optical perform rod which may be manufactured as disclosed in U.S. Pat. No. 4,217,027. In this patent, a film of glass-forming material is deposited on the interior of a glass cylinder which is rotated in a glass lathe. The glass cylinder is then collapsed into a short, thick rod or preform which is about 1/2 inch thick and several feet long. The preform is then drawn into an elongated thin filament of a single or a graded index of refraction across its thickness.
Such preforms require complicated processing steps and repeated batch-type handling and increase the cost of the ultimate fiber. Thus, the preform may constitute 75% of the cost of the fiber. Furthermore, since fiber is drawn from a rod of given volume, the length of the fiber which can be drawn is limited. This increases the number of optical couplers and amplifiers needed to connect a number of relatively short segments into a very long signal path.